1. Field of the Invention
This invention relates to documents of value, such as bank notes, checks, passports, ID cards or the like with increased fitness for circulation, to a security paper for producing them, and to a method for producing said security paper and such documents of value.
2. Description of the Background Art
Bank notes are usually made of so-called security papers consisting of cotton fibers and having special security features, such as intaglio printed motifs, hologram patches and watermarks. A bank note's period of circulation depends on the stress. Certain denominations are preferably used in trade and thus have a smaller period of circulation due to the stronger load through environmental influences. Environmental influences are for example attack by different chemical substances, such as perspiration, fat, oil, lyes, acids, etc. Particularly smaller note values are subject to increased wear. The main cause of the restricted period of circulation for bank notes is considered to be (besides premature soiling) initial tear of the bank note in the edge area.
U.S. Pat. No. 3,661,700 describes a coated, reinforced paper produced by coating a support comprising a net of a longitudinally oriented polypropylene film with a mixture of cellulose-containing fibers and/or other fibers and mineral and/or organic pigments or fillers, and binders. Since the net is used for reinforcement, it must have the same dimensions as the paper to be reinforced therewith.
British patent no. 3453 describes a paper for bank notes, papers of value and the like containing a fine, open-mesh fabric with or without figures, patterns or numbers. The open-mesh fabric is incorporated into the paper by being passed into the paper stock while the stock is being moved over a screen on its way from the tank to the press rolls, before it reaches the press rolls so that the fabric can be pressed into the flowable paper stock. In this case, too, the fabric has the same dimensions as the paper.
British print 1 219 643 relates to the production of reinforced paper whereby a netlike or meshed reinforcement material is incorporated by different methods. The reinforcement material has the same dimensions as the paper.
AU-PS 488,652, for example, has proposed making bank notes completely from a plastic substrate. Said plastic substrates do have higher initial tear resistance than paper substrates but the plastic substrate's tear propagation resistance is extremely low in comparison with a paper substrate. Further, with a plastic bank note there can be no use of customary and proved security elements such as portrait watermark and windowed security thread. Also, the steel gravure printing customary in the bank note field, which serves as an additional tactile authenticity mark due to the relief arising from the inking, leads only to a flat, hardly perceptible relief on plastic substrates.
The above-described prior art security papers moreover share the disadvantage that the incorporation of an all-over net or the use of a plastic substrate causes the special properties, such as sound and feel, of bank note paper to be completely lost.